Another factor that may add complexity will be the optics. I'm guessing that most projectors aren't designed to focus down to a 4" or 6" square area. Getting it to do so will require modifying the optics. Doing so without adding significant distortion may be non-trivial.

Update: So only 3 people showed up to the meeting Adam, Ed, Kelly, Steve

Software: Apparently there is a setting in skeinforge that outputs the model into an svg. Note 1 svg. It has some software that lets you select the different layers to show. Examination of the svg in note pad showed that all the layers are in separate paths (duh). We've determined that if we write a script to parse the paths and save them into it's own svg we can use a slide show to display the layer. Kelly said we could work on this script.

Projector: needs to be xga or higher

Frame: looking for a 8-9" pyrex baking pan

Resin: Need to place an order to experiment with. Ed suggested contacting Tra-con about a sample of uv cure adhesives.Edit: Ed ordered some resin

Today, I got around to shooting it with an Edipower 10W 405 nm LED. The LED was driven with a current limited lab power supply at 1.04A and just over 10 Volts. I'd previously bought the LED off eBay, and can't seem to find the original datasheet for it. At the time, I was interested in using it to expose dry film photoresist for PCB artwork. It actually works quite well for that exposing a 6" square area in perhaps a couple minutes through a piece of white copy paper. If memory serves correctly, it puts out somewhere around 1W at 405nm into a 120 degree beam. The LED is 9 emitters, 3 parallel strings of 3 in series, spread out over less than 1 cm^2.

This LED isn't a toy like the little keychain lights for checking for counterfit bills. From 10 feet away, you can see glow from fluorescent labels, and a bit of glow from other things. It is moderately hazardous, and although borderline UV, the usual hazards of UVA and deep blue lasers apply, such as increased risk of cataracts. You can feel a perceptable wamth on the back of your hand. Think about what it can do to your eyes if used carelessly. We'll definitely want a gaurd like a piece of orange or red fluorescent plastic to view the work and a safety switch connected. That isn't as bad as it sounds, as you don't want to expose the unused resin anyway.

A four minute exposure at 5cm distance produced a slighly tacky, but stable suface (tacky but incompletely exposed after about 2 minutes) on a white business card. The deposit was 0.035" (almost 1mm) thick.

This equates to an exposure of about 100 mJ/cm^2 for a 1mm thickness without the benefits or losss of any optics.

While there are shorter wavelength LEDs, and the polymers are likely more senstive, they are also less efficient electric to optical. This is an older LED and it might be possible to find a 385nm emitter with about the same optical efficiency. If the chemistry is at all similar to the dry film resist, they might be twice as sensitive.

The bottom line is an LED source is probaly viable with a DLP projector engine. If not this one, higher power ones are available.

Yes, the optics will probably require modification to focus closer. Specifically, the lens will probably need a shim to move it further from the DLP. To experiment, we can probably use longer screws and a strip of metal as a spacer, with some tape to seal dust out of the gap.

The pyex pan we'd be looking for would have a relatively clear area for the portion an image will be formed through. This would mean an 8*11 o 9*13 without a pyrex logo or other raised print in the middle. Generic rather than branded may be better as long as it is a borosilicate glass instead of soda-lime glass. If this turns out to be a pain, epoxying polycarbonate sides with appropriate strain relief woul be a viable option.

I suspect for the DLP projectors we have at the space a much smaller pyrex should work, I think 3x4 is about the biggest we'd want to try and still have decent resolution. If we buy a higher-res projector for this at some point, then we'll want to go bigger.

I got what I think we need for the software side running Pronterface with projector mode. I believe if we either whip up a vertical mount or get a 1st surface mirror we can try some exposures. This is a quick test with a model of Reddit.

Currently I get a printer not online when I select projector, it wants an arduino to talk to it seems, I'll see if I can get it to believe I have an arduino driver / printer for it to talk to.

I saw this DLP Lightcrafter system (link) in a TI booth at a conference and thought it was pretty neat. They were using it in conjunction with a camera for 3D image scanning. The DLP would project various patterns, which highlighted shape differences. The camera was at an angle to the projected image.

The close in (~2 feet) image projected in the example in the booth was pretty sharp and a width of about a foot or so.

Anyway, one of the things mentioned was that you could replace the RGB LED light engine with more powerful one. That made me think, what if you replaced it one that used UV LEDs (assuming these exist). How bright does the UV light have to be anyway for the resin to congeal?

Thorpedo wrote:....Anyway, one of the things mentioned was that you could replace the RGB LED light engine with more powerful one. That made me think, what if you replaced it one that used UV LEDs (assuming these exist). How bright does the UV light have to be anyway for the resin to congeal?

From what I've read you want as much UV as daylight provides at a minimum to have a reasonably quick curing time. Thicker layers take more, and or longer. Most DLPs have a Mecury vapor based lamp, which is a pretty good UV source. In the projector the color wheel is a UV filter, so for a dedicated 3D printer it is typically removed.